NASA Delays First Flight of New SLS Rocket Until 2019 (arstechnica.com)

schwit1 writes: Despite spending almost $19 billion and more than thirteen years of development, NASA today admitted that it will have to delay the first test flight of the SLS rocket from late 2018 to sometime in 2019. "We agree with the GAO that maintaining a November 2018 launch readiness date is not in the best interest of the program, and we are in the process of establishing a new target in 2019," wrote William Gerstenmaier, chief of NASA's human spaceflight program. "Caution should be used in referencing the report on the specific technical issues, but the overall conclusions are valid." The competition between the big government SLS/Orion program and private commercial space is downright embarrassing to the government. While SLS continues to be delayed, even after more than a decade of work and billions of wasted dollars, SpaceX is gearing up for the first flight of Falcon Heavy this year. And they will be doing it despite the fact that Congress took money from the commercial private space effort, delaying its progress, in order to throw more money at SLS/Orion.

Comments

Re:What governmen brought to the table

[cheesybagel]

Solids have horrible failure modes for a manned space flight platform. Not to mention they are inefficient like heck. The only reason to use solids is because you're indirectly funding ICBM tech. I'm not sure I agree with the LOX/H2 thing though. It kind of depends on the vehicle and engine design. But it is true hydrocarbons are a lot more dense and hence result in less vehicle manufacturing costs.

Re:What governmen brought to the table

[Rei]

That's not the reason you don't use it for a first stage. The disadvantages of hydrolox (which are numerous) are offset by its incredible specific impulse. But for a first stage, specific impulse doesn't matter that much, while thrust matters a lot. Thrust is in large part proportional to fuel density, as a turbopump sweeps out a fixed volume per rotation, so the denser the fuel, the more mass (and generally all else being equal, energy) it pumps per rotation.

Another aspect is that first stages are big, meaning that cost is more important than specific impulse. By contrast, when dealing with an upper stage, a small increase in mass has a huge increase in first stage size, and since first stages are so large and expensive, that's a big cost. So you generally want a higher ISP upper stage. With the caveat that "storability" requirements for engines that need to restart can shift the balance; because hydrogen is so deeply cryogenic it's difficult to store for protracted lengths of time. Also, the longer you plan to have a stage in usage without maintenance, the more you tend to favour simple propellants over high performing ones, particularly when you're dealing with small, light engines. So for example if you have an interplanetary probe you'll tend to favour a self-pressurizing hypergolic system so that you only have to rely on a couple valves working, even though self-pressurizing propellant tanks are heavier and hypergolics tend to be lower specific impulse. Engines that are smaller still are often monoprops for an even greater degree of simplicity.